Step motors are a driving device that may control a rotation angle of a motor to be constant by using a simple controlling circuit which may accurately control a location of a subject of the driving without including a separate location sensor.
A step motor of the related art is driven by using a basic angle control scheme, which is referred to as a full step or half step control mode. When the step motor is controlled by using the basic angle control scheme, a shaft may vibrate as a motor rotates to a basic movement angle at a relatively large angle for every pulse input. The micro step control scheme is a technique that controls a step motor by increasing resolution of a rotation angle in a method of driving a step motor by dividing a step into angles (a micro step) smaller than the basic movement angle to drive a step motor. According to the micro step control, a decrease in a rotation angle of a motor per step may reduce shaft vibration and increase the resolution of the motor rotation angle. However, even when the micro step driving method is used, a location error of about ±5% may occur in general.
In order to compensate for the error, a magnetic sensor or an optical sensor that may sense a location of a rotator may be placed in a step motor, and thus a location error caused by driving a step motor may be sensed and compensated for. However, when a magnetic sensor or an optical sensor is placed in a step motor, a size of a driving unit may increase according to an external diameter of the sensor, and it may be difficult to place a microscopic sensor on a printed circuit board (PCB).